The present invention relates to a method and apparatus for picking the top or the bottom sheet, as desired, from a stack of sheet documents to be scanned in a document scanning device such as an all in one document scanner, copier and facsimile machine or for stand alone scanners, copiers and facsimile machines and the like. As used herein, the term "document scanning device" is therefore intended to encompass all types of devices in which documents are fed to be scanned and the teachings of this disclosure are accordingly not necessarily limited to all in one or stand alone document scanners, copiers and facsimile machines.
Automatic document feeders, particularly for all in one products such as generally described above, require a mechanism which must pick in the correct order of document sheets which are stacked. For facsimile transmission of a multi-page document, the first page picked by the automatic document feeder should be transmitted first to in accordance with conventional first page out facsimile transmission protocol. Conversely, when copying a document, it is conventional to pick and copy the last sheet of the document first in order to assure that the printed output order is correct. This problem is resolved if the user is willing to insert the input documents in one order, e.g., face down for facsimile transmission and in a different order, e.g., face up for simplex (one side) sheet copying. For truly universal operation of an all in one product, not only single sided (simplex) copying, facsimile transmission and scanning should be achievable by the automatic document feeder, but also double sided (duplex) copying, facsimile transmission and document scanning should be achievable without the user being required to stack the document differently depending on the function to be performed.
The present invention is directed to an automatic document feeder which has the capability of picking single document sheets to be scanned with the same mechanism which can be easily controlled to either pick from the top or the bottom of the document stack depending on the function to be achieved and without changing the position of the mechanism on the scanning device.